Hydraulic mechanism



June 11, 1968 w. susgs 3,387,453

HYDRAULIC MECHANISM Filed March 4, 1966 2 Sheets-Sheet l INVENTOR MM J'WGJ ATTRNEYJ June 11, 1968 w. M. sucses HYDRAULIC MECHANISM 2 Sheets-Sheet Filed March 4, 1966 RESElVd/R V Juana/4 INVENTOR Rue: roll ATTORNEY;

United States Patent 3,387,453 HYDRAULIC MECHANISM Willie M. Suggs, 3113 Herbert Ave., Orlando, Fla. 32805 Filed Mar. 4, 1966, Ser. No. 531,720 8 Claims. (Cl. 60-52) ABSTRACT OF THE DISCLOSURE Apparatus for controlling fluid pressure to a lift cylinder by regulating the speed of a fluid pump. The apparatus includes a fluid actuated means directly connected to the motor which drives the pump 'and such fluid actuated means is controlled by a valve means which is movable between first and second positions by fluid pressure.

This invention relates to mechanical movements, more particularly the application of forces, especially through hydraulic mechanism.

While the invention is adapted for use in various mechanisms, it is particularly adapted for the operation of hydraulic forklifts.

Forklifts have for many years been in widespread usage for moving heavy and bulky loads within a relatively localized area such as a plant. Heretofore, in situations where an operator stands on the platform of the forklift, it has been necessary for a second operator to remain adjacent to the driver operating mechanism in order to operate the forklift including controlling its speed.

The present invention provides a remote control by means of which a single operator may position himself on the platform of the forklift and control its operation without the necessity of an additional operator.

Mechanism for accelerating the pump motor for a hydraulic forklift responsive to an increase in load, 'as for example during the raising of the lift, has heretofore been known. However, in order for such mechanism to rapidly permit reduction of speed of the pump motor to idling speed, the means which regulates the speed control has had to be selected in accordance with the load to be raised. Otherwise, delay in reduction of speed and other undesirable functioning has resulted.

The present invention is an improvement on the general mechanism described in that the speed control operates rapidly and responsively without regard to the weight of the load.

Accordingly, it is the object of the present invention to provide a remote control which may be mounted on and adjacent to the forklift.

A further object is 'a provision 'of an improved hydraulic feed mechanism by means of which the direction of movement of the forklift may be controlled and in which the speed in a given direction may be predetermined and controlled by simple control elements mounted on and adjacent to the forklift.

A further object is an automatic hydraulic feed mechanism which provides a predetermined movement of controlled elements in two directions.

These and other objects of the invention will become apparent from the following description in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective of a forklift truck illustrating the application of the invention thereto;

FIG. 2, a plan view of the arrangement of the hydraulic mechanism of the apparatus of FIG. 1;

FIG. 3, a fragmentary, enlarged detail of the control mechanism; and,

FIGS. 4, 5, and 6, schematics illustrating the operation of the mechanism in response to operation of the Up and Down buttons, and with both out of operation.

3,387,453 Patented June 11, 1968 Briefly stated, the present invention includes a hydraulically controlled mechanism having a main piston connected to speed control mechanism and normally positioned for idling. The piston is movable in response to the application of hydraulic force in order to move the speed control to a desired position of increased speed. Plow to and from the main piston is controlled by a check valve piston normally in a position in which flow to the main piston is closed. Upon an increase in pressure the hydraulic fluid moves the check valve piston in order to permit the hydraulic fluid force to be applied to the main piston, the check valve simultaneously closing the return valve from the main piston.

Upon a predetermined decrease in the fluid pressure in the main line the check valve closes the inlet to the main piston and opens its outlet. As a result the main piston promptly responds to a pressure decrease in the main line and is moved to a position in which the pump is at idling speed.

With further reference to the drawings, FIGS. 1 and 2 illustrate a typical application of the invention. This includes a forklift truck 10 having an internal combustion or other type motor 11 which drives a fluid pump motor 12. Mounted on the front of the truck is a hydraulic cylinder 13 to which lift 'arms 14 are connected in conventional manner. The motor 11 has its speed controlled by a control rod 15.

The pump motor 12 discharges hydraulic fiuid into a main line 20 and has a return and sump line 21. The line 20 may communicate with the lift cylinder 13 by branch line 22 and with a feed control 23 by branch line 24. From the feed control 23 a return line 25 is connected with the supply sump. In order that appropriate control of the lines may be easily effected, switches, preferably electrically controlled, are mounted on the lift at 27. These switches operate a valve 27' including valve means 28, 28 controlling the connection of line 22 to line 20 and line 21, respectively. Valve means 29 controls the connection of line 21 to line 20.

These switches may be arranged in various ways. A convenient way is to provide an Up button and a Down button. Depressing the Up button 50, as in FIG. 5, results in closing valve means 29 and opening valve means 28. Releasing the Up button, as in FIG. 4, results in closing valve means 28 and opening valve means 29. Depressing the Down button 51 while the Up button is released, as in FIG. 6, results in opening valve means 28' and 29.

The feed control means 23 is illustrated in detail in FIGS. 2 and 3. As shown, it includes supply and return lines 24 and 25 to which reference has been made. Supply line 24 communicates with bore 30 having a floating piston or check valve 31 which is loosely mounted therein. On the opposite side of piston 31 a check valve spring 32 abuts one face of the check valve piston 31 and the end wall 33 of the bore 30.

The bore 30 has openings 35, 36 which are spaced slightly further apart than the piston 31. Hence, the piston 31 may be moved to cover either of the openings 35 and 36. The check valve piston 31 preferably is so arranged as to move approximately 4 of an inch from a first position as indicated in FIG. 3 to a second position. The check valve piston fits loosely so that some leakage between it and the bore 30 occurs when it is under fluid pressure. Hence, when the fluid pressure decreases only slightly the spring immediately causes the check valve piston to return to its initial position.

As a result of the foregoing, the feed control operates independently of the weight of the load carried by the fork.

Opening 35 is connected to a supply line 38 and opening 36 to the discharge line 39 of an enlarged bore 40.

3 Mounted in the bore 40 is a piston 41 which is normally held in substantially adjacent relationship to the end wall 44 of the bore 40 by means of a spring 42 the end of which abuts the opposite face 43 of the piston 41 and of the remote end wall 45 of the bore 40.

Speed control rod is connected by rod 15' and link 15 to piston 41 whereupon movement of the piston substantially away from the end wall 44 produces an increase of speed of the motor 11.

A limit rod 33' is connected to the end wall 33 of the bore and a limit stop collar 4-2 is mounted within the bore 40.

The switch means 27 is preferably mounted on the lift platform in a position convenient for the operator. In the operation of the device, when the operator desires to move the lift upwardly, he depresses the Up button 50. This closes valve means 29 to the sump and opens 28 to the lift cylinder. Simultaneously, the increase in pressure moves check valve 31 to uncover opening 35 and to cover opening 36 thereby causing the fluid pressure to build up against piston 41. This causes the piston and control rod 41 to move to the left in FIG. 3 of the drawings and thereby increases the motor speed. As the motor speeds up and the pressure further increases, the lift is raised.

When the left has reached the height desired, the operator releases the Up button. This immediately closes valve means 23 to the lift cylinder and opens valve means 29 to the sump. Since valve means 28 is closed the lift is maintained in the selected raised position. Since the sump is open the pressure in the line 20 and in the branch line 24 to the feed control immediately drops. This re sults in check valve 31 being returned to its initial position in which inlet line 38 is closed and outiet line 39 connected with the line 25 to the sump is open. This permits the spring 42 promptly to return the piston 41 and the connected control rod 15 to idling position.

Upon depression of the Down button, valve means 28 to the lift cylinder is open, and line 20 is connected to line 21, thereby permitting fluid in the lift cylinder to return to the sump by means of line 21 to complete a cycle of operation.

Accordingly, it will be appreciated that the invention provides a rapidly responsive remote control by means of which the operator can raise a lift, or other hydraulic device, hold the lift in raised position and lower the lift.

The invention permits these functions to be carried out with a high level of responsiveness despite a wide varia tion in the load on the lift.

Where a particular embodiment has been described it will be understood by those skilled in the art that the invention is not limited thereto but only as described in the following claims.

What is claimed is:

1. In a speed control for a hydraulic pump which discharges fluid under pressure to a fluid actuated mechanism, means for driving the pump, speed control means for the driving means, and fluid lines from the discharge and inlet of the pump for communication with the fluid actuated mechanism, the improvement comprising:

(a) fluid actuated means controlling the speed control means, said fluid actuated means connected to said speed control and having an inlet for communication with said pump discharge line, and an outlet for communication with said pump inlet line, whereby said fluid actuated means may be subjected to fluid at a pressure corresponding, respectively, to that in said pump discharge and inlet lines, said fluid actuated means being movable between first and second positions, responsive to the pressure of said fluid, and

(b) fluid actuated valve means for the fluid actuated means, said fluid actuated valve in in a first position covering said inlet to prevent the flow of fluid to said fluid actuated means and in a second posiion covering said outlet while uncovering said inlet to permit flow of fluid to the fluid actuated means for substantially preventing flow of fluid through said outlet, stop means for preventing movement of said valve means past said second position, s: id fluid actuated valve means communicating with the pump inlet and discharge lines and being movable by fluid pres sure between the first and second positions.

2. The invention of claim 1, and first valve means controlling the passage of fluid from the pump discharge line to the fluid actuated mechanism, second valve means controlling the passage of fluid from the pump discharge line to the pump inlet, and third valve means controlling the passage of fiuid from the fluid actuated mechanism to the pump inlet.

3. The invention of claim 2, and switch means for operating said valve means, said switch means alternately opening said first valve means and closing said second and said third valve means, closing said first and third valve means and opening said second valve means, and closing said first and opening said second and third valve means.

4. The invention of claim 3 in which said switch means is mounted on the fluid actuated mechanism whereby an operator on said mechanism may control its operation.

5. The invention of claim 1 in which the fluid actuated means is a first piston mounted for reciprocation in a first bore and the fluid actuated valve means is a second piston mounted for reciprocation in a second bore.

6. The invention of claim 1 in which said fluid actuated valve means is a piston mounted in a bore for reciprocation therein, spring means mounted intermediate an cud of the bore and the end of the piston which is remote from the inlet of the fluid actuate-d valve means, said spring means tending to urge said piston toward said inlet, said piston being loosely fitted within the bore, Whereby upon the reduction of pressure upon the piston from the pump, the spring may immediately return the piston to the position in which the inlet to the fluid actuated means is closed by the piston of said fluid actuated valve means.

7. The invention of claim 5 in which the bore of said fluid actuated means is provided with a collar for limiting the movement of said piston in said bore, the fluid actuated means is connected to the speed control by a rod, and spring means is provided adjacent to the rod for urging the piston away from said coilar.

8. The invention of claim 5 in which said first piston has first spring means intermediate it and the end of said first bore which is remote from the pump discharge line, and said second piston has second spring means in said second bore urging said second piston toward the position covering the inlet to the fluid actuated means.

References (fitted UNITED STATES PATENTS 2,061,530 11/1936 Wile 6052 2,643,515 6/1953 Harsch. 2,655,903 10/1953 Tyler 9l459 2,697,329 12/1954 Eichler 9l-459 2,931,305 4/1960 Stratton 6019 X 2,977,769 4/ 1961 Troche.

EDGAR W. GEOGHEGAN, Primary Examiner. 

